Deshawn Isabelle, 15, is charged as an adult in connection with a robbery and sexual assault on a train in Chicago. He is being held on a $1 million bond.

In court Thursday, prosecutors said Isabelle's mother recognized him from surveillance photos and took him to the police station to turn himself in.

In court Thursday, prosecutors said surveillance video from the CTA Blue Line train shows Isabelle grabbing the 41-year-old woman from behind, sexually assaulting her and robbing her around 3 p.m. Monday on a CTA Blue Line train near the Oak Park stop.

"The defendant continued to punch victim repeatedly about her head, face and body. Defenden repeatedly kicked victim and stomped on her while making monetary demands of the victim," Joe DiBella, assistant state's attorney, said.

The defendant allegedly stuck his hands inside the woman's jeans and penetrated her sexually, prompting the sexual assault charge. The two were the only passengers in that train car, prosecutors said, and the offender is seen exiting at Cicero.

He took the woman's iPhone, prosecutors said, and $2,000 in cash the victim was going to wire to her family in Thailand.

"Defendant indicated he used the money he took to spend on junk food, his high school graduation costs, and Air Jordan jumpsuits," DiBella said.

Isabelle, who has a juvenile record that includes a conviction on misdemeanor theft, signed a written confession police said.

The victim was hospitalized overnight with a concussion, official said.